1. Field of the Invention
The invention relates to a melt-blow head with a rectilinear row of nozzle bores arranged in a nozzle bar of a nozzle assembly, said nozzle bores serving to produce endless filaments formed from a melt, said nozzle bores being associated with blowing slots, in the form of longitudinal slots, of two slot-plates for feeding blowing air at an angle to the nozzle bores and to which nozzle bores the melt is fed, via melt feed pipes from one or more distribution bars and via melt pipes in a distribution block of the nozzle assembly, to those nozzle bores in the nozzle bar which are to be fed with the melt, wherein the blowing slots are supplied with the blow air through blow-air feed pipes in a blow-air feed element via blow-air distribution bores.
2. Description of Background Art
Such a melt-blow head is described and presented in German patent specification DE 103 58 170 B3. In the known melt-blow head, the melt feed pipe leads from a melt pipe via a lateral inlet and via a removable connector as well as via a redirecting means in a substantially vertical direction to a distributor distributing the melt to individual nozzle bores, the nozzle assembly being fixed in a defined position with respect to the slot-plates and being removable therefrom in an approximately vertical direction. In said publication, the blow air is supplied via spaces between the blow-air feed element and the nozzle assembly. A variability of the spinning width of the known melt-blow head is not discussed in the aforementioned patent specification.
Known from European patent application EP 1 486 591 A1 is a device for the production of filaments, more particularly from thermoplastic material, the filaments issuing from spinning nozzle openings of a spinning nozzle plate. A distribution device is provided for distributing a supplied plastic melt. Positioned downstream of the distribution device is at least one exchangeable distribution plate. Positioned downstream of the distribution plate is an exchangeable spinning nozzle plate. The spinning width formed by the distribution openings in the exchangeable distribution plate is smaller or greater than the spinning width provided by the distribution device. By means of the at least one exchangeable distribution plate, the spinning width of the distribution device can be reduced or increased to the final spinning width. Therefore, the desired final spinning width is adjustable through replacement of the distribution plate. The supply and/or adaptation of a blow-air addition according to different spinning widths is not discussed in the aforementioned document.
Generally, the continuous production of melt-spun nonwoven fabrics, which include both spunbond nonwovens in the conventional sense and also microfibre nonwovens, manufactured in meltblown systems, is accomplished by systems with predetermined working widths or spinning widths, such systems not being subject to any defined standard. There are, however, certain industry-typical specifications; for example, typical spinning widths are 1600, 2600, 3200 and 4200 mm. In a second working step, the correspondingly produced nonwoven fabrics are then assembled to the final width, it being the case, however, that, usually, the spinning widths cannot be fully utilized, with the result that, in the worst case, up to 50% of the roll width is wasted.
In the case of the adjustment of the spinning width via exchangeable distribution plates, as known from European patent application EP 1 486 591 A1 (see above), the plastic melt is distributed over a reduced or increased width of the downstream, likewise exchangeable spinning nozzle plate. In the case of such narrowing or widening, however, it must be expected that the plastic melt will not be uniformly distributed across the entire spinning width on both sides of the narrowing or widening and that, inside a hole field of the spinning nozzle plate, there will be a different plastic-melt distribution which may find expression in differences in the weight per unit area of the end product across the working width as well as in filament breaks because of excessive or insufficient supply of melt, this possibly having a negative impact on productivity.
If one wishes to vary the effective spinning width, for example by positioning the melt-blow head at an angle in relation to the production direction of the nonwoven fabric which is to be produced, this would necessitate correspondingly flexible connections of the supply lines for water and power as well as for plastic melt and blow air.
Furthermore, with both of the aforementioned possibilities for adjusting the effective width of the produced nonwoven fabric webs, it is necessary also to adapt the feed width of the hot blow air to the spinning width, because said blow air, in the form of hot compressed air, represents an immense cost factor in production. It is, therefore, desirable to reduce the consumption of hot blow air in order to cut costs. In the known prior art (see above), however, this topic is either not addressed at all or (e.g. in cases where the entire system or at least parts thereof is/are positioned at an angle) this requires complex measures which necessitate the complete conversion/exchange of the associated blow-air supply.